Cloud storage systems provide users with storage services with large capacity, high access efficiency, and reasonable prices. Nevertheless, the users who use cloud storage services will lose absolute control over the data once they upload files to the CSP. As it is well known, CSP (cloud server provider) is not reliable. Whether the data on the cloud is with integrity has become a problem worth considering. Under the public cloud storage environment, this study defines a company, organization or organization as a group, and the group is managed by the person in charge who can help the users in the group using the cloud storage service conveniently. In this scenario, to solve the problem of user data integrity verification in the same group, a data integrity verification scheme is proposed for group users in this study. To assist users in one group to carry out a series of operations, an entity named Agency is proposed. In this scheme, the design of the tag is based on IBE (identity-based encryption), which frees the users from complicated certificate management. In the integrity verification process, by adopting random sampling, the performance overhead of the system is greatly reduced. With the help of the random oracle model, the security of the proposed scheme is proved. A practical experiment validates the feasibility of the scheme in the end.